This is part six of a series examining the challenges confronting the NATO alliance.

Germany is pledging to become a more powerful military force inside NATO, with Berlin’s ambassador to Washington telling Fox News Digital that the country is ready to assume greater responsibility for European security after decades in which the United States carried much of the alliance’s military burden.

"Germany is stepping up — we heard the call!" German Ambassador to the United States Jens Hanefeld told Fox News Digital in an exclusive interview.

Chancellor Friedrich Merz has said Germany’s armed forces should become the strongest conventional army in Europe, a goal Hanefeld said is now backed by Berlin’s new military strategy.

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"Russia’s illegal war of aggression has shaken old certainties in Europe and Germany as the international rules we have relied on are being challenged," Hanefeld said. "This changes the strategic environment we operate in."

"Today, Germany is Ukraine’s largest supporter," Hanefeld said in written answers. "Germany’s decision to become Europe’s strongest conventional army, well anchored in the NATO alliance, is an ongoing commitment."

Germany’s historic military shift

The shift marks a historic turn for a country whose postwar military identity was built around restraint. 

After World War II, West Germany was allowed to rearm only within a Western alliance framework, joining NATO in 1955 and building the Bundeswehr as a force embedded in collective defense rather than independent German power. For decades after reunification, Germany relied heavily on the U.S. security umbrella and often lagged behind NATO spending targets, feeding repeated American complaints that Europe’s largest economy was not pulling its weight.

Russia’s full-scale invasion of Ukraine in 2022 forced Berlin to begin rethinking that posture. Then-Chancellor Olaf Scholz called the shift a "Zeitenwende," or turning point. Merz is now seeking to turn that phrase into a long-term military buildup.

In Germany, Hanefeld said, the changes underway are often described as a "Zeitenwende," but he acknowledged that the transformation does not come easily given the country’s history.

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Trump–Merz tensions complicate NATO politics

The effort is unfolding against a backdrop of public friction between President Donald Trump and Merz, a dispute that a U.S. defense expert warned could complicate critical decisions on deterring Russia.

The tension escalated after Merz criticized Washington’s handling of the Iran war, saying the United States was being "humiliated" by Iran’s leadership in negotiations and questioning the Trump administration’s exit strategy. Trump fired back by accusing Merz of being soft on Iran’s nuclear program, even though Merz has said Iran must not obtain a nuclear weapon.

The dispute quickly spilled into NATO politics. Trump later threatened to review possible U.S. troop reductions in Germany and said Merz should spend more time ending the war in Ukraine and "fixing his broken country" than commenting on Iran.

Then Merz added another irritant. Speaking to a young audience in Germany, he said he would not advise his children to live, study or work in the United States "today," citing America’s changing social climate, while also saying he remained "a great admirer of America," but "My admiration isn’t growing at the moment."

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Retired Rear Adm. Mark Montgomery, a senior fellow at the Foundation for Defense of Democracies and former U.S. European Command official, told Fox News Digital that Merz was wrong to speak that way about Trump at a moment when Germany needs Washington’s support. 

"Talking trash about the president at a meeting with school kids in Germany is not professional diplomacy, and especially a president who is well-known to be prickly as President Trump," Montgomery said. "Germany is not the big country in this relationship, the United States is, and Merz needed to show more discipline as a national leader." 

Montgomery said those tensions risk affecting hard security decisions, including long-range strike capabilities in Germany.

He criticized recent U.S. moves to delay or potentially cancel a rotational deployment of long-range strike systems to Germany, which he said would have included Tomahawk, SM-6 or Precision Strike Missile capabilities. Reuters reported in May that Germany’s defense ministry said there had been no "definitive cancellation" of the deployment.

"Both of these are bad decisions being made by our Department of Defense," Montgomery said. "These are weapons systems that are incredibly important to deterring Russia."

He said the goal is not to fight Russia in Poland, the Baltics or the Suwałki Gap, but to prevent Moscow from attacking in the first place.

"And those long-range strike weapons are a big part of that. And I’m very disappointed in our Department of Defense," Montgomery said.

A source with knowledge of the matter said that despite briefings about possible decreases in U.S. involvement, the U.S.–Germany defense relationship remains strong and cooperation remains close.

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Europe’s future defense industrial base

"Germany developing a large, impressive defense industrial base is good for NATO, it’s good for Western security, and it’s even good for our primes," Montgomery said, arguing that Germany, not Poland, France or the United Kingdom, is most likely to become the "beating heart" of Europe’s future defense industrial base.

Germany has long been central to the U.S. military presence in Europe. Hanefeld pointed to Ramstein Air Base, Landstuhl Regional Medical Center and the training area in Grafenwöhr as examples of Germany’s continuing importance to American power projection and NATO deterrence.

"These facilities serve U.S. national security interests and U.S. military personnel and further NATO’s ability to deter and defend," he said. "I am confident: NATO will remain transatlantic at its core, but will become more European over the next decade."

At the 2025 NATO summit in The Hague, allies agreed to invest 5% of GDP annually in defense and defense-related spending by 2035, including core military spending and broader security investments. Merz said at the time that the decision was meant to safeguard "freedom, security and prosperity," according to the German government.

Hanefeld said Germany is already moving to meet that standard, saying Berlin will increase defense spending to 5% of GDP "well before" 2035 and recruit almost 100,000 new active-duty soldiers into the Bundeswehr.

He also pushed back against U.S. critics who argue that Germany and other European allies are still not carrying their fair share of the defense burden. Hanefeld said Germany has signed more than 380 contracts worth more than $33 billion with U.S. defense companies to procure and manufacture fighter jets, transport helicopters, air defense systems and ammunition.

"It’s a down payment on the transatlantic future and on our political commitment to shift the burden for deterrence and defense to Europe," Hanefeld said.

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Defending NATO’s eastern flank

One of Germany’s most visible commitments is its permanent brigade in Lithuania, expected to include around 5,000 German military and civilian personnel. The Bundeswehr says the force is intended to become fully operational for the defense of NATO’s eastern flank in the Baltic region within three years.

Hanefeld called the brigade one of Germany’s "signature efforts" to reassure Baltic allies that NATO "will defend every inch of allied territory."

For Germany, the change is not only about money. It is a political and cultural break with decades of caution about military power. For the United States, it is also a test of whether the ally long criticized by Trump and other U.S. leaders for underspending can now become the European backbone Washington has demanded.

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Hanefeld said that is exactly where Berlin intends to go.

"NATO will remain transatlantic at its core," he said, "but will become more European over the next decade."

U.K. Defense Secretary John Healey resigned Thursday after clashing with Prime Minister Keir Starmer's government over military spending, dealing the British leader a setback weeks before a critical NATO summit to include President Donald Trump.

Healey's departure stemmed from a dispute over the delayed Defense Investment Plan (DIP) — the government's long-promised roadmap for military investment and readiness — and as NATO allies face renewed pressure from Trump to boost defense spending.

"John Healey’s resignation is a seismic moment for the government and the Ministry of Defense," Royal United Services Institute (RUSI) Senior Associate Fellow Ed Arnold told Fox News Digital.

"For the government, it creates a sequence of political headaches in terms of a replacement, and trying to get the Defense Investment Plan published."

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Healey had been in intense, late-stage negotiations with Starmer and Chancellor of the Exchequer Rachel Reeves over the scale and timelines of the DIP.

Starmer reportedly refused to set out a timeline to reach 3.5% of gross domestic product (GDP) on defense by 2035 — a promise he made to Trump at last year's NATO summit — and would not commit to a firm date for reaching 3%.

Instead, Starmer offered Healey a deal to spend 2.68% of GDP on defense by 2030, up only marginally from 2.6% next year, Reuters reported.

"You have been unable, and the Treasury has been unwilling, to commit the resources that the nation needs to defend the country," Healey wrote to Starmer in his resignation letter, warning that the financial constraints would "make the country less safe," the outlet reported.

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"If the delay to the Defense Investment Plan was already undermining the government’s credibility on defense, John Healey’s resignation has blown a hole in its side," professor Kevin Rowlands of the RUSI defense and security think tank told Fox News Digital.

"The immediate consequence is not just political embarrassment for No. 10, but a significant loss of planning certainty at a time when the British Armed Forces, the Ministry of Defense, and industry really need clarity on what will be funded, and when," he added.

The political fallout is expected to reverberate across the Atlantic, where Washington has increased pressure on European allies to fulfill their defense obligations. Trump has frequently criticized NATO alliance members as "free riders."

On June 3, Secretary of State Marco Rubio also told the House Foreign Affairs Committee that the upcoming Ankara summit would be the "most important meeting" in NATO’s history because there are some things "that need to be cleared up and fixed."

He added, "The United States is still in the NATO alliance, and we'll be there."

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However, U.S. officials have made it clear that patience is wearing thin.

"Ahead of next month’s NATO summit, POTUS has been clear: Allies must fulfill their commitment to spending 5% of GDP on defense," U.S. Ambassador to NATO Matthew Whitaker posted on X this week.

Furthermore, a U.S. official noted that a U.K. funding package far lower than 18 billion pounds ($23 billion) would send a highly "negative" signal to Trump ahead of the Ankara meeting, according to The Times.

Starmer has pledged to lift spending to 3% in the next Parliament but Healey’s exit has exposed that the current strategy leaves the U.K. lagging behind key allies. By comparison, Germany plans to spend 3.7% of its GDP on defense by 2030.

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"Healey knows the threats we face, he knows the capabilities and shortfalls the armed forces have, and if he believes that the financial settlement is not enough to keep the country safe — to the extent that he cannot honorably stay in post — then we are in trouble," Rowlands added.

"While the impact will mainly be felt on Whitehall, the international implications are severe with a NATO summit just three weeks away," Arnold noted.

This is part six of a series examining the challenges confronting the NATO alliance.

As President Donald Trump presses NATO allies to shoulder more of Europe's defense burden, countries closest to Russia are moving fastest — while some of Western Europe's biggest economies face growing pressure to catch up. 

Retired Rear Adm. Mark Montgomery, senior director at the Foundation for Defense of Democracies and former deputy director for strategy, policy and plans at U.S. European Command, said the shift is already visible across the alliance.

"Europe is clearly stepping up, but they're stepping up by geographic variation," Montgomery told Fox News Digital.

"If you ask me who's doing the most, the Eastern Europeans are clearly."

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Montgomery pointed to the Baltic states, Poland, Romania and Bulgaria as countries moving aggressively to strengthen deterrence against Russia.

His assessment comes as NATO allies work toward a new defense spending benchmark agreed at the 2025 summit in The Hague, which calls on members to invest 5% of GDP in defense and security-related spending by 2035, including 3.5% for core defense requirements and 1.5% for defense-related infrastructure and security investments.

John Deni, a research professor at the U.S. Army War College, said the trend shouldn't be surprising. 

"Given the threat of Russia, allies in the East are acquiring capabilities more quickly, and they're spending even more than allies in the West," Deni told Fox News Digital. "This shouldn't surprise us because they're the ones closest to the threat."

Deni noted that many eastern allies are rapidly purchasing equipment already available on the market rather than waiting years for domestic defense programs to mature.

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The transformation is visible across NATO's eastern and northern flanks. Poland has become one of the alliance's largest military spenders, Romania is increasing defense investments, and Finland and Sweden have added advanced military capabilities to NATO following their accession.

Secretary of State Marco Rubio praised Finland and Sweden Thursday at the Senate Foreign Relations Committee hearing, using them as examples of allies strengthening the alliance.

"Sweden and Finland have actually contributed because they brought their own defense industry, their own advanced technology," Rubio said. "They have been great partners." 

Romanian Foreign Minister Oana-Silvia Ţoiu echoed that message in an interview with Fox News Digital following an emergency U.N. Security Council session convened after a Russian drone strike injured civilians in the Romanian city of Galați.

"We do agree with President Trump on the need to increase budgets," Ţoiu said.

Ţoiu said Romania raised defense spending to 2% of GDP during Trump's previous term and plans to allocate "an average of 3.4 percent" next year through military procurement and strategic infrastructure investments.

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"We have launched initiatives that are directed at the eastern flank because it is increasingly more clear that that needs to be protected," she said.

She argued that Romania's role extends beyond national defense.

"We need better deterrence, better defense capabilities there in order to ensure our responsibility in protecting not just the Romanian border, which is the longest border to the war, but also it is in the same time a European border and the border of the Allied territory," Ţoiu said.

For frontline states, the urgency is driven by geography as much as politics. Romania shares a border with Ukraine and repeatedly has dealt with Russian drones entering its airspace. Poland has become one of NATO's top military spenders, while the Baltic states are racing toward defense expenditures approaching 5% of GDP.

Montgomery said the eastern flank's urgency contrasts sharply with the pace in much of Western Europe.

Among the continent's five largest economies, and despite a slight decrease in military spending in 2025, the U.K. remains the largest investor relative to GDP, with 2.4%, trailed by Germany (2.3%), Spain (2.1%), France (2%) and Italy (1.9%), according to the Stockholm International Peace Research Institute (SIPRI).

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"The Germans are the one country, I think, with a large economy that is starting to make the right kind of investments."

Germany, he argued, could become the backbone of Europe's future defense industrial base.

"Germany developing a large, impressive defense industrial base is good for NATO, it's good for Western security, and it's even good for our primes," Montgomery said.

German Chancellor Friedrich Merz has embraced higher defense spending and backed NATO's new spending goals, positioning Berlin as a potential hub for Europe's future defense industrial base as allies seek to reduce long-term dependence on the United States.

But despite rising defense budgets, experts warn Europe remains heavily dependent on American military capabilities.

Barak Seener, a senior fellow at the Henry Jackson Society, said Europe still relies on the United States for many of the systems required to fight a modern war.

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"Europe is heavily dependent on NATO for its strategic airlift and sea lift, its air-to-air refueling, its cyber capabilities, its space assets, its intelligence, surveillance and reconnaissance," Seener said.

Without those capabilities, he warned, European forces would struggle to maintain situational awareness during a major conflict.

Montgomery said Europe faces three major challenges: expanding military capacity, rebuilding its defense industrial base and developing high-end support capabilities that have long been provided by the United States.

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"When you are freeloading for 30 years, you create enormous deficits in terms of people, equipment, technology and know-how," he said.

"The primary forces to defend Europe should be European," he said. "The United States should provide additional forces that allow maneuver and offensive operations."

Montgomery also criticized reported Pentagon deliberations over delaying long-range strike deployments to Germany and reconsidering future Tomahawk missile sales, arguing the systems are critical for deterring Russia.

"The goal here is not to fight Russia in the Baltics or in Poland. The idea here is we want to deter Russia from even trying to attack."

Looking ahead, Montgomery remains optimistic about NATO's future.

Montgomery predicted Europe will continue increasing defense spending and expanding its defense industrial base, while the alliance benefits from steadier transatlantic relations.

"I think you'll have a U.S. president that probably doesn't provoke the Europeans as much. You'll have Europe that's investing more," he said.

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He also predicted NATO Secretary-General Mark Rutte would be remembered for helping hold the alliance together through a period of significant change.

"I think five years from now, NATO will be stronger," he said. "And I hope we have Ukraine in there."